1. Field of the Invention
The subject disclosure relates to wave dissipation systems, modular units for use in wave dissipation systems and methods of constructing the same, and more particularly to the construction of breakwater systems using a plurality of modular elements, and still more particularly to a breakwater system which in certain embodiments includes interlocking precast, preformed and reinforced elements.
2. Background of the Related Art
Beaches experience erosion in response to energy resulting from waves that impinge on the shoreline. A variety of breakwater systems and designs have been previously used with varying degrees of success, to inhibit the deterioration of beaches. Many of the previous breakwater systems have been constructed in areas having relatively low tidal ranges. In regions where tidal ranges exceed one meter, the stage of the tide also plays an important role on the vertical distribution of wave energy on the beach face.
In regions of relatively high tidal range, low-profile modules are often ineffective. If the devices are placed on the upper part of the beachface to shield the shore from waves at high water, the devices are left high-and-dry as the tide falls to low water level. If they are placed to intercept waves at low water, then they are too deep at high water to effectively shield the beach from incoming waves.
Since beaches are made of granular material, they are subject to change in direct response to the ability of the wind, waves and currents to transport the sediment. The process of erosion is an accounting problem related to sand transport by wind, waves and currents. Simply stated, when more beach material leaves a section of shore than it receives, the volume loss is described as erosion. When more beach material enters a section of shore than it loses, the volume gain is described as accretion. Since the capacity of a wave to transport sand is related to its size, then variations in wave size similarly relate to variations in the transport capacities of wave fields. Large waves, or strong wave-driven currents, have a greater capacity to transport beach material than small waves or weak wave-driven currents. By obstructing a portion of an incoming wave field, the capacity of the wave field to transport sediment is also diminished. The resultant is that less sand is removed from the beach than would be expected from the previously unobstructed waves. This is the main principal in the use of breakwaters for inhibiting erosion.
U.S. Pat. Nos. 3,875,750; 4,407,608; 4,498,805; 4,722,598; 4,776,725; 4,801,221; 4,896,996; 5,011,328; 5,120,156; 5,129,756; and 5,238,326 represent an evolution of concepts that have provided partial solutions to some coastal areas of the world. Although some of these systems have provided valuable insights to the art, none have proven to be universally successful.
Some of the prior art has been directed toward trapping the littoral transport system. Others have been located further offshore to intercept wave energy before it reaches the shore. Much of the offshore systems have been composed of relatively small modules that are placed side-by-side and stacked to produce a submerged barrier parallel to the shoreline. Scour at the base of individual modules often causes them to shift, rotate forward, and/or sink into the seafloor. Stacks of multiple modules are massive, tend to sink into the seafloor rapidly and are difficult to remove or re-orient for breakwater modification or upgrade.
Despite these prior are systems and designs, there is still a need for an economical breakwater design and installation method which is long lasting and reusable. Moreover, it is further advantages to provide a modular unit for use in a breakwater system which can be made from precast concrete and formed remotely and later placed at the beach site. Still further, there is still a need for a rapidly constructible breakwater system which is adaptable to a variety of beach erosion problems and can address sea-level rise conditions.